In recent years, phase-change memories which use chalcogenide materials as recording materials have been studied actively. A phase-change memory is one type of resistance-change memories that store information by exploiting such behavior that recording materials between electrodes have different resistance states.
A phase-change memory stores information by exploiting such behavior that a phase-change material such as Ge2Sb2Te5 has different resistivity in its amorphous and crystalline states. The resistance is high in the amorphous state and is low in the crystalline state. Thus, a read is performed by biasing a voltage difference between both ends of a device to measure electric current flowing in the device and determining whether the device is in a high resistance state or a low resistance state.
In phase-change memories, data programming/erasing is performed by changing electrical resistance of a phase-change film to a different state using the Joule heat generated by electric current. Reset operation (that is, operation of changing the electrical resistance to a high resistive amorphous state) is performed by biasing a large amount of current for a short period to fuse the phase-change material and then quickly decreasing the current to rapidly cool the phase-change material. On the other hand, set operation (that is, operation of changing the electrical resistance to a low resistive crystalline state) is performed by biasing an amount of current sufficient for maintaining the phase-change material at its crystallization temperature for a long period. Theoretically, the phase-change memories are ideal for reduction of memory cell size because the amount of current required for changing the state of a phase-change film decreases along with reduction of memory cell size. Due to this, studies on phase-change memories have been conducted actively.
Moreover, PTL 2 discloses an example of a phase-change memory in which a channel layer extending to a direction perpendicular to a substrate is formed between stripe-shaped stacked gates, phase-change materials being in contact with the facing channel layers are separated by an insulator film, and a select transistor that controls the current flowing in the respective channels independently is used so that information can be recorded in the respective separated phase-change material layers independently.
As a method of realizing the integration of memory which uses a resistance-change device, PTL 1 discloses a configuration in which a plurality of gate electrode materials and a plurality of insulator films are alternately stacked to form a stacked structure, a plurality of through-holes is formed in a collectively patterning manner so as to penetrate through the entire layer, and a gate insulator film, a channel layer, and a phase-change film are deposited and patterned inside the through-holes. Moreover, PTL 3 discloses an example of a resistance-change memory rather than a phase-change memory in which a channel layer extending in a direction perpendicular to a substrate is formed between stripe-shaped stacked gates and a resistance-change material is formed in a region interposed between the facing channel layers.